Patent GB-486620-A (GB)
Title: Improvements in or relating to the manufacture of articles with protective or resistant surfaces or surface parts
IPC: B22D19/00
Filed: 1937-02-01
Abstract: 486,620. Coating by electrophoresis. NAAMLOOZE VENNOOTSCHAP WALLRAMIT HANDEL MAATSCHAPPIJ. Feb. 1, 1937, No. 2965. Convention date, Jan. 30, 1936. [Class 41] [Also in Group XXII] Tools such as stamping and pressing tools and printing plates, having sharp contours and having resistant surfaces are produced by forming the surface layer by electrophoretic deposition of a metal or alloy in a former, and then uniting a supporting metal or alloy therewith. The resistant material may comprise iron, steel, chromium, nickel, cobalt, molybdenum, tungsten, or carbides, borides, nitrides, or silicides of chromium, tungsten, molybdenum, or the like. In the production of a printing- plate, a former is produced from sheet tin, zinc, lead, soft copper or brass or the like, from a cliche or stereotype in known manner. The form is coated electrophorotically with tungsten, chromium, nickel, steel or iron, and lead, zinc, iron, or other backing is cast in. The form is removed chemically, thermally or mechanically. A strengthening layer, such as of copper or iron, may be electrolytically deposited before casting. The first layer, especially when of chromium, may be coated with a thin layer of gold or silver before the second deposit is applied, this intermediate layer being applied by burning in a solution of a gold or silver compound. A separating layer such as arsenic, or silver iodide or sulphide may initially be applied to the former. In the production of a form for use in a glass pressing operation, or tools for producing articles from rubber or artificial masses such as artificial rubber, wood or resins, resistant surface layers of hard metal borides, carbides, &c. are provided. A model is made from soft metal, or from artificial rubber, wood, or resin such as " Galalith " (Registered Trade Mark). An impression is taken with a paste of soapstone, steatite, or porcelain earth, which is dried and burnt. Finely powdered metal carbides or borides are applied singly or in a mixture, by electrophoretic deposition, the carbides or borides being in suspension in very finely divided condition in a liquid such as methyl alcohol. The article is suspended in the bath and acts as cathode and is surrounded by the anode. Voltages of about 400 are employed. The suspension is stirred during the deposition operation, which lasts from between a few minutes to an hour. The layer is dried, heated, and sintered. The form may be filled during sintering with a viscous paste, such as clay with a volatile medium such as ethylene trichloride or carbon tetrachloride, the binder being evaporated, the form weighted with a fireclay plate, and sintered. Alternatively fireclay chamotte, quartz powder or magnesium oxide can be pressed in. After sintering, the filling is removed, and an iron alloy is cast in before complete recrystallization of the carbide or boride layer, preferably before the layer has cooled below red heat, or below the melting point of the carrier metal or alloy. The rear side of the electrophoretically deposited layer may be electrolytically coated with nickel, cobalt, iron or steel before or after sintering. A further carbide or boride layer may be applied if cracks appear after the first heating. According to the Specification as open to inspection under Sect. 91, the resistant layer may be produced by electrodeposition, vaporization, cathode dispersion in vacuo, or thermal decomposition of carbonyl compounds of tungsten, molybdenum, chromium, nickel, cobalt, &c. The process is applicable to the production of any articles having resistant surfaces. This subject-matter does not appear in the Specification. as accepted.